Temperature dependence of photoresponse in p-type GaAs/AlxGa1-xAs multiplequantum wells: Theory and experiment

Bound-to-continuum (BC) absorption and photoresponse in p-type quantum well infrared photodetectors are investigated theoretically and experimentally as a function of polarization and temperature. Using the 8 x 8 envelope-fun ction approximation model, the quantum well electronic structure and wave f unctions are calculated and then the BC absorption curves are obtained on a n absolute scale as a function of photon energy, light polarization, and te mperature. Since optimum absorption obtains for structures with the second light-hole (LH2) state at the top of the well, a nonoptimized long-waveleng th infrared structure and an optimized mid-wavelength infrared structure we re grown by molecular-beam epitaxy and their characteristics measured to te st the theory. Whereas the optimized sample has the LH2 resonance at the to p of the well, the nonoprimized sample has light-hole quasibound states wit hin the heavy-hole continuum. This different placement of the light-hole sl ates produces a different temperature and polarization dependence of the ab sorption process in these samples. Our temperature-dependent photoresponse measurements corroborate most of the theoretical findings with respect to t he long-wavelength threshold, shape, and polarization and temperature depen dence of the spectra.